Electric circuit interrupter



H. BURMElsTER ELECTRIC CIRCUIT INTERRUPTER Filed May 5, l1937 Aug. l5, 1939.

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Patented Aug. 15, 1939 PATENT OFFICE ELECTRIC CIRCUIT INTERRUPTER Hermann Burmeister, Berlin-Spandau, Germany,

assignor to `General Electric Company, a corporation of New York 'Application May 5, 1937, Serial No. 140,901

Germany June 20, 1936 2 Claims.

My invention relates to electric circuit interrupters, more particularly to'those of the gas-expulsion type wherein the arc formed upon opening of the circuit is substantially confine in an arc,chamber and reacts with the arc chamber walls to produce an arc-extinguishing gas.

Circuit interrupters of this type, more particularly electric switches, have been proposed wherein the arc chamber is composed of an artificial resin such as a carbamide resin. Although a material of this character is adapted to yield an .appreciableamount of arc-extinguishing gas when subjected to the arc, the mechanical strength of the material may be inadequate in case the switch is subjected to'unusual stresses due, for example, to inaccuracies in manufacture such as slight misalinement of the contacts. In such cases during the switch opening or closing operations the resin may be subjected to severe lateral stresses and cracked or fractured.

The principal object of my invention is the provisionI of an improved arc-'extinguishing chamber which is both simple and rugged in construction, of good insulating characteristics and adapted to produce an adequate amount of arcextinguishing gas upon opening of the circuit.

My invention will be more fully set forth in the following description referring to the accompanying drawing, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming apart of this specification.

' structure that is both .mechanically strongby the resin by molding into a laminated structure comparatively thin plates or sheets of `ber, or an equivalent material, and the artificial resin. As is well known in the art, the fiber is also adapted to produce an arc-extinguishing gas under the influence of the heat of the arc. The arc chamberwalls therefore are composed of a unitary reason of the fiber reinforcement' and has generally uniform gas-yielding characteristics.

There is illustrated by Fig. 1 an electric circuit breaker or switch comprising a fixed Contact structure generally indicated at l and a coacting movable tubular contact 2. The contacts (Cl. 20o- 149) generally indicated at 3 through which the arc 5 is drawn upon opening of the circuit.

The arc chamber 3 in the present instance comprises a sleeve-like laminated structure open at opposite ends for allowing the contact 2 to operate therethrough and engage the fixed contact i. The arc chamber is suitably secured with respect/to the iixed contact terminal structure 4 and has positioned concentrically thereof an insulating bolt 5 in alinement with the center of the tubular Contact 2. Accordingly an annular arc space 3 is formed between the fixed and movable contacts during the opening or downward movement of the Contact 2.

The walls of the arc chamber 3 and the bolt 5 are composed of sheets of ber 6, preferably alternating with an articial resin l, such as a carbamide resin, for example, so as to form a unitary laminated structure. In view of the fact that fiber possesses a high percussion yielding strength, comparatively thin plates or sheets of the order of magnitude of 0.01 to 0.1 millimeter in thickness, are yadequate for reinforcing the articial resin body. As illustrated, this arrangement permits the thickness of the resin between sheets to exceed appreciably the thickness of a single sheet. Preferably the resin is molded with respect to the fiber sheets, so that the fiber is practically embedded in the resin. Absorption of moisture by the ber in such a case does not take place to any extent and, therefore, there are no appreciable variations in shape or dimensions of the arc chamber due to warping.

As previously pointed out, the quality or quantity of the arc-extinguishing gas is not adversely 40 point is that `fiber can easily be machined and Vadapted quite readily for uniting with the resin.

For example, as illustrated in Fig. 2, the fiber can beV perforated as indicated `at 8 so that during '50 the molding operation the resin is permanently locked,to the ber so that the resultant resin- 'liber structure is a uniform homogeneous unit.

The fiber strip shown in Fig. 2 represents a fiber strip ofthe central insulating bolt. it of course being understood that the ber, as in the case of the main arc chamber, can be in the form of concentric sleeves or similar reinforcing forms.

It should be understood that my invention is not limited to specic details of construction and arrangement thereof herein illustrated, and that changes and modications may loccur to one skilled in thel art without departing from the spirit of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1.- An electric circuit interrupter of the gasexpulsion type comprising arc forming means, a composite insulating structure of the gas-evolving type dening an arc chamber therefor, said composite insulating structure being composed of laminationsof mechanically strong thin ber plates and an artiiicial Vresin disposed in interleaving relation, both of which are adapted to yield an arc-extinguishing gas when subjected to arcing, said resin being molded to embed said sheets therein in substantially parallel spaced relation so that said composite insulating structure constitutes a mechanically strong unit that is eiective notwithstanding gradual disintegration of said resin to yield arc-extinguishing gas, said sheets having a thickness which is substan- `tially less than that of the intervening resin material.

2. An electric circuit interrupter of the gasexpulsion type comprising arc-forming means, and insulating means of the gas-revolving type dening a pressure-confining arc chamber therefor, said insulating means being composed of Ya'.

composite, mechanically strong laminated structure of thin fiber sheets having perforations and a carbamide resin alternating with said Aber sheets, said resin being molded to embed said sheets therein so that said'resin is initially acted upon by said arc to yield arc-extinguishing gas, the thickness of said resin between said sheets being greater than -tlie thickness of a single sheet.

HERMANN BURMEISTER. 

